Evaluation of the accuracy of conventional and digital implant impression techniques in bilateral distal extension cases: a randomized clinical trial.

BACKGROUND: This clinical study aims to evaluate the accuracy of the conventional implant impression techniques compared to the digital impression ones in bilateral distal extension cases. METHODS: A total of 32 implants were placed in eight patients missing all mandibular posterior teeth except the first premolars. Each patient received a total of four implants, with two implants placed on each side, in order to provide support for three units of screw-retained zirconia restorations. Following osteointegration, the same patient underwent two implant-level impression techniques: Conventional open-tray impressions CII (splinted pick-up) and digital implant impressions DII with TRIOS 3 Shape intraoral scanner. The accuracy of impressions was evaluated utilizing a three-dimensional superimposition analysis of standard tessellation language (STL) files. Subsequently, the scan bodies were segmented using Gom inspect software to measure three-dimensional deviations in a color-coding map. Data were statistically analyzed using the Kruskal Wallis test and then a post-hoc test to determine the significance level (P < 0.05). RESULTS: The study revealed that higher angular and positional deviations were shown toward distal scan bodies compared to mesial ones for both impression techniques. However, this difference was not statistically significant (P > 0.05). CONCLUSION: Splinted open-tray conventional impression and intraoral scanning implant impression techniques have demonstrated comparable accuracy. TRIAL REGISTRATION: Clinical Trials.gov Registration ID NCT05912725. Registered 22/06/ 2023- Retrospectively registered, https://register. CLINICALTRIALS: gov .

Trueness of Extraoral Digital Impressions for Full-Arch Implant Impressions-In Vitro Study.

Direct scanning of silicone impressions is a valid technique. However, studies in implant-supported rehabilitations are lacking. This in vitro study aims to compare the trueness of impressions obtained with two types of silicone and their corresponding stone casts, using two laboratory scanners in a full-arch implant rehabilitation. A master cast with six dental implants was scanned with a 12-megapixel scanner to obtain a digital master cast. Ten implant impressions were made using two silicones (Zhermack and Coltene) with the open-tray technique. The impressions and stone casts were scanned by two extraoral scanners (Identica T500, Medit; and S600 ARTI, Zirkonzhan). Trueness was assessed by comparing linear and angular distances in digital casts with the master cast. A p < 0.05 significance level was considered. The results showed that for the linear measurements, 72% were higher than the master cast measurements, and no consistent pattern was observed in the angular measurements. The greatest deviations were detected between the most posterior implants, with mean values ranging between 173 and 314 µm. No significant differences were found between scanners. However, differences were observed in the distances between silicones (46.7%) and between impressions and stone casts (73.3%). This work demonstrates that the direct scanning of silicone impressions yields results comparable to those obtained from scanning gypsum casts in full-arch implant-supported rehabilitation.

TRUENESS OF INTRAORAL SCANNERS IN DIFFERENT SCAN PATTERNS FOR FULL-ARCH DIGITAL IMPLANT IMPRESSIONS.

The optimal scan pattern for full-arch digital implant impressions remains to be determined. This study aimed to analyze the effects of different scan patterns on the trueness of intraoral scanners for full-arch digital implant impressions. A maxillary plaster model with four implant analogs was employed as the master model. Scan bodies were attached to the master model and scanned with a laboratory scanner to obtain reference data. Test scans were obtained using three different scan patterns with Cerec Primescan and Trios 3. Each test data was superimposed onto the reference data. The trueness was assessed by determining the 3D distance and angular deviations between the test and reference data. Significant differences in 3D distance deviation were detected among the scan patterns for both scanners. Significant differences in angle deviation were detected among the scan patterns for the Cerec Primescan, whereas it was not substantial for the Trios 3. Cerec Primescan exhibited superior trueness across all scan patterns compared to Trios 3. The zigzag pattern resulted in more accurate scans for the Cerec Primescan, while both the zigzag and occlusal-palatal-buccal patterns showed higher accuracy for the Trios 3.

Comparison of Intraoral Scanning Modes in Three Distinct Full- Arch Digital Implant Impression Scenarios: An In Vitro Study.

PURPOSE: The purpose of this study was to analyze the effect of scanning modes on the accuracy of the Trios for full-arch digital implant impressions. MATERIALS AND METHODS: The trueness and precision of the intraoral scanning mode (IOSM) and the intraoral edentulous scanning mode (IOEM) of the Trios were evaluated in three edentulous models, each featuring 4, 6, and 8 implant analogues. Reference scanning data were obtained by scanning each model with a desktop scanner. Each model was scanned 10 times using the IOSM and IOEM modes of the Trios to establish the test groups. The scan bodies in the test and reference scans were isolated and exported in the reverse engineering program. The scan bodies in each group were superimposed with the corresponding reference scan (trueness) or with each other (precision). The overall 3D deviation between the aligned scan bodies was computed by the root-meansquare (RMS) values. RESULTS: As a result of the trueness and precision evaluation, no significant difference was found between scanning modes in any of the models. When comparing models, the 8-implant model showed significantly lower trueness than the 4-implant model. However, it also exhibited significantly higher precision when compared to both the 4-implant and 6-implant models. There were no significant differences in other pairwise comparisons between the models. CONCLUSION: Trueness and precision values were similar between the IOSM and IOEM groups across all the models. An increase in the number of implants in complete edentulous arches may have a negative impact on digital impression accuracy.

Influence of intraoral scanning coverage on the accuracy of digital implant impressions - An in vitro study.

OBJECTIVES: To evaluate the influence of intraoral scanning coverage (IOSC) on digital implant impression accuracy in various partially edentulous situations and predict the optimal IOSC. METHODS: Five types of resin models were fabricated, each simulating single or multiple tooth loss scenarios with inserted implants and scan bodies. IOSC was subgrouped to cover two, four, six, eight, ten, and twelve teeth, as well as full arch. Each group underwent ten scans. A desktop scanner served as the reference. Accuracy was evaluated by measuring the Root mean square error (RMSE) values of scan bodies. A convolutional neural network (CNN) was trained to predict the optimal IOSC with different edentulous situations. Statistical analysis was performed using one-way ANOVA and Tukey's test. RESULTS: For single-tooth-missing situations, in anterior sites, significantly better accuracy was observed in groups with IOSC ranging from four teeth to full arch (p < 0.05). In premolar sites, IOSC spanning four to six teeth were more accurate (p < 0.05), while in molar sites, groups with IOSC encompassing two to eight teeth exhibited better accuracy (p < 0.05). For multiple-teeth-missing situations, IOSC covering four, six, and eight teeth, as well as full arch showed better accuracy in anterior gaps (p < 0.05). In posterior gaps, IOSC of two, four, six or eight teeth were more accurate (p < 0.05). The CNN predicted distinct optimal IOSC for different edentulous scenarios. CONCLUSIONS: Implant impression accuracy can be significantly impacted by IOSC in different partially edentulous situations. The selection of IOSC should be customized to the specific dentition defect condition. CLINICAL SIGNIFICANCE: The number of teeth scanned can significantly affect digital implant impression accuracy. For missing single or four anterior teeth, scan at least four or six neighboring teeth is acceptable. In lateral cases, two neighboring teeth may suffice, but extending over ten teeth, including contralateral side, might deteriorate the scan.

Clinical assessment of maxillary screw-retained implant prosthesis fabricated from digital versus conventional full- arch implant impression. A randomized controlled clinical trial.

OBJECTIVES: To evaluate the peri-implant marginal bone loss (MBL) and prosthodontic complications of maxillary screw-retained implant prosthesis fabricated from digital versus conventional full- arch implant impression. MATERIAL AND METHODS: 28 participants with edentulous maxillary arches were randomly selected and enrolled in two equal groups; Group I conventional impression group (CIG) and Group II Digital impression group (DIG). All patients were rehabilitated with maxillary screwretained implant prosthesis retained by 6 implants. Peri-implant MBL and prosthodontic complications and were registered at 6, 12, and 24 months (m). Data was collected and statistically analyzed. RESULTS: Regarding the effect of time, there was a statistically significant increase in MBL at 6, 12 and 24 m follow-up periods (P<.001). As for the effect of groups, there was no statistically significant difference in MBL between CIG and DIG at 6, 12 and 24 m where P value was 0.083, 0.087 and 0.133 respectively. Prosthetic complications were recorded 19 times in the conventional group and 12 times in the digital group with no significant difference between both groups (P=.303). CONCLUSION: Digital full -arch implant impression is a reliable impression technique and may represent an alternative to conventional impression technique in the fabrication of maxillary screw-retained implant prosthesis.

Does intra-oral scan improve the impression accuracy of full-arch implant-supported prostheses: A systematic review and meta-analysis.

OBJECTIVES: The present study aimed to systematically review the studies comparing the accuracy of intraoral scan (IOS) and conventional implant impressions (CI) in completely edentulous patients. MATERIALS AND METHODS: Electronic searches were performed in PubMed, Embase and Cochrane CENTRAL up to December 1, 2023. Clinical studies and in vitro studies reporting the accuracy of digital full arch impressions were included. The primary outcome is the 3-dimensional deviations between the study reference models. A risk of bias assessment was performed for clinical studies. A stratified meta-analysis and a single-armed meta-analysis were conducted. RESULTS: A total of 49 studies were included, with 8 clinical studies and 41 in vitro studies. For comparison between IOS and conventional impressions, studies were categorized into two groups based on the different measurement methods employed: RMS and CMM. In studies using RMS, the result favored the IOS in the unparalleled situation with the mean difference of -99.29 µm (95% CI: [-141.38, -57.19], I2 = 81%), while the result was opposite with the mean difference of 13.62 µm (95% CI: [10.97, 16.28], I2 = 26%) when implants were paralleled. For different brands of IOS, the accuracy ranged from 76.11 µm (95% CI: [42.36, 109.86]) to 158.63 µm (95% CI: [-14.68, 331.93]). CONCLUSIONS: Accuracy of intraoral scan is clinically acceptable in edentulous arches, especially for unparalleled implants. More clinical studies are needed to verify the present finding.

Accuracy of impression methods through the comparison of 3D deviation between implant fixtures.

AIM: To compare the accuracy of three impression methods by comparing the distance between the reference points of the implant fixture, especially in curved maxillary anterior teeth. MATERIALS AND METHODS: Implant fixtures were placed in the maxillary central incisor and canine regions. A maxillary master cast was made using a model scanner and 3D printer. Ten impressions were taken from the three experimental groups constructed (group P: pick-up impression coping; group I: scan body with an intraoral scanner; group B: bite impression coping). The distance between the reference points, the angle between the scan bodies, and displacement of the 3D surface area were measured. RESULTS: The distances between the reference points were significantly different between groups I and B in the maxillary incisors, and between group P and the other two groups in the maxillary canines. Group P had the least amount of displacement in both fixtures. Both fixtures showed the highest displacement in group B. Displacement of the 3D surface area in the maxillary incisors showed no significant difference between the groups. There was a significant difference in the maxillary canines between groups P and I. CONCLUSIONS: In the present study, all three implant impression methods showed changes in the position and angle of the fixture compared with the master cast. The highest accuracy was shown by the impression method using the pick-up impression coping, but the impression method using the intraoral scanner also showed clinically acceptable accuracy. It should be noted that errors may occur when taking impressions using a bite impression coping.

A digital approach to create a virtual implant preliminary cast for the fabrication of a splinted framework and custom open tray for multiple implants impression making: A dental technique.

A digital approach is described for fabricating a splinted framework and custom open tray for the impression of multiple implants based on a virtually created implant cast with the digital prediction of the future impression coping positions. In this technique, impression copings to be used in the definitive impression-making process were digitally scanned and aligned to a preliminary cast using installed protective caps of screw-retained abutments as references, which resulted in a virtual cast that offers information both about the impression coping positions and their surrounding tissues and could allow a splinted framework and custom open tray to be digitally designed and fabricated. Creation of a virtual cast through digital technologies eliminates the traditional manual splinted framework and custom tray fabrication procedures. Additionally, only one set of impression copings and analogs is needed in this technique, thereby reducing treatment time and cost. It also offers a splinted framework and custom open tray with consistent quality.

Comparison of 3D accuracy of three different digital intraoral scanners in full-arch implant impressions.

PURPOSE: This in vitro study aimed to evaluate the performance of digital intraoral scanners in a completely edentulous patient with angled and parallel implants. MATERIALS AND METHODS: A total of 6 implants were placed at angulations of 0°, 5°, 0°, 0°, 15°, and 0° in regions #36, #34, #32, #42, #44, and #46, respectively, in a completely edentulous mandibular polyurethane model. Then, the study model created by connecting a scan body on the implants was scanned using a model scanner, and a 3D reference model was obtained. Three different intraoral scanners were used for digital impressions (PS group, TR group, and CS group, n = 10 in each group). The distances and angles between the scan bodies in these measurement groups were measured. RESULTS: While the Primescan (PS) impression group had the highest accuracy with 38 µm, the values of 104 µm and 171 µm were obtained with Trios 4 IOSs (TR) and Carestream 3600 (CS), respectively (P = .001). The CS scanner constituted the impression group with the highest deviation in terms of accuracy. In terms of dimensional differences in the angle parameter, a statistically significant difference was revealed among the mean deviation angle values according to the scanners (P < .001). While the lowest angular deviation was obtained with the PS impression group with 0.185°, the values of 0.499° and 1.250° were obtained with TR and CS, respectively. No statistically significant difference was detected among the impression groups in terms of precision values (P > .05). CONCLUSION: A statistically significant difference was found among the three digital impression groups upon comparing the impression accuracy. Implant angulation affected the impression accuracy of the digital impression groups. The most accurate impressions in terms of both distance and angle deviation were obtained with the PS impression group.

Comparison of the Accuracy of a Mounting Fixture for Dental Implants for Implant Position Transfer and Open-Tray Implant Level Impression-An In Vitro Study.

The accuracy for the implant position transfer of a mounting fixture and a standardized open-tray implant level impression was compared. Ten aluminum master models with four implant analogs placed in different angulations were fabricated. By performing an open-tray implant level impression stone casts were produced. The master models and stone casts were scanned (comparison group one) using a laboratory scanner. Deviations in the scan body surface were determined in the form of mean (absolute) point distances and (signed) surface distances. The same procedure was performed with a screwed transfer and by fixing the posts of the mounting fixture (comparison group two). The mounting device was applied to each master model and scanned in a fixed and detached state (comparison group three). In a point comparison, the open-tray implant level impression showed mean deviations of 43.6 µm and a mounting fixture of 44.6 µm with no significant differences (p < 0.05). There were significant differences between groups two and three. The angulation of the implants had no effect on the accuracy. In a surface comparison, the open-tray implant level impression showed mean deviations of 36.0 µm and a mounting fixture of 2.0 µm (p > 0.05). Within the limits of this study, the mounting fixture transferred the implant position with the same accuracy as the open-tray implant level impression with respect to point deviations.

EPA Consensus Project Paper: Accuracy of Photogrammetry Devices, Intraoral Scanners, and Conventional Techniques for the Full-Arch Implant Impressions: A Systematic Review.

PURPOSE: The objective of this systematic review was to evaluate and compare the accuracy of digital impression techniques and conventional methods for full-arch implant impressions. METHODS: An electronic literature search in the databases Medline (Pubmed), Web of Science, and Embase was performed to identify in vitro and in vivo publications (between 2016 and 2022) directly comparing digital and conventional abutment-level impression techniques. All selected articles passed through the data extraction procedure according to defined parameters in inclusion and exclusion criteria. Measurements on linear, angular and/or surface deviations were performed in all selected articles. RESULTS: Nine studies met the inclusion criteria and were selected for this systematic review. 3 articles were clinical studies and 6 studies were in vitro. Accuracy difference mean values of the trueness up to 162+/-77µm between digital and conventional techniques were reported in the clinical studies and up to 43µm in laboratory studies. Methodological heterogeneity was observed in both, in vivo and in vitro studies. CONCLUSIONS: Intraoral scanning and photogrammetric method showed comparable accuracy for registering implant positions in the full-arch edentulous cases. A tolerable implant prosthesis misfit threshold and objective misfit assessment criteria (for linear and angular deviations) should be verified in clinical studies.

Characteristics of intraoral scan bodies and their influence on impression accuracy: A systematic review.

OBJECTIVE: The aim of this systematic review was to evaluate the influence of the characteristics of intraoral scan bodies (ISBs) on the accuracy of intraoral scanning. MATERIALS AND METHODS: An electronic search was conducted through PubMed (MEDLINE), Scopus and Cochrane Library, up to March 2023. The literature search intended to retrieve all relevant clinical and in vitro studies about the effect that the various properties of ISBs may have on the accuracy (trueness and precision) of intraoral scanning. Only publications in English language were selected with animal studies, case reports, case series, technique presentation articles and expert opinions being excluded. RESULTS: A total of 28 studies met the inclusion criteria and were included in this systematic review. They were published between 2019 and 2023 and were all in vitro studies. Among the parameters described, the scan body material, position, geometry, height, diameter, and fixation torque were evaluated. The most common materials used for ISBs were polyetheretherketone (PEEK) and titanium alloys. The diameter and position of ISBs seemed to affect the trueness of implant impressions. Subgingival implant position and decreased ISB height affected negatively the trueness of scanning. Geometrical characteristics of ISBs also affect the implant impression accuracy, especially the bevel location and the types of designing modifications. CONCLUSIONS: The characteristics of the currently used ISBs vary widely and the available scientific evidence is not yet conclusive about the optimal design of ISB. The implant impression accuracy achieved by any of the studied parameters is encouraging. Clinical studies are however necessary for more concrete conclusions. CLINICAL SIGNIFICANCE: ISBs play a vital role in the digital workflow and influence significantly the accuracy and fit of implant restorations. More clinical trials are needed in order to conclude to the optimal characteristics of ISBs which would further enhance the success of the restorations.

Comparing the accuracy of full-arch implant impressions using the conventional technique and digital scans with and without prefabricated landmarks in the mandible: An in vitro study.

OBJECTIVES: This study evaluated the accuracy of digital implant impressions with or without prefabricated landmarks compared with the conventional method in the edentulous mandible. METHODS: An edentulous mandibular stone cast with implant abutment analogs and scan bodies in FDI #46, #43, #33, and #36 served as the master model. The scans captured with intraoral scanners (IOS) were divided into four groups: IOS-NT (no landmarks + Trios 4 scanner), IOS-NA (no landmarks + Aoralscan 3 scanner), IOS-YT (landmarks + Trios 4 scanner), and IOS-YA (landmarks + Aoralscan 3 scanner) (n=10). Landmarks were attached to the scan bodies with resin to improve scanning fluency. Conventional open-trayed technique (CNV) was performed with the 3D-printed splinting frameworks (n=10). The master model and conventional castings were scanned using a laboratory scanner, and the former served as the reference model. Overall distance and angle deviations between scan bodies were measured to determine trueness and precision. The ANOVA or Kruskal-Wallis test compared CNV group to scans without landmarks, while a generalized linear model analyzed scan groups with and without landmarks. RESULTS: Compared to the CNV group, the IOS-NA and IOS-NT groups showed higher overall distance trueness (p=0.009), and precision (distance, p<0.001 and angular, p<0.001). With landmarks, the IOS-YA group had higher overall trueness (distance, p<0.001 and angular, p<0.001) than the IOS-NA group, and the IOS-YT group has higher distance trueness (p=0.041) than the IOS-NT group. Moreover, the precision in distance and angle was significantly improved for IOS-YA and IOS-YT groups, compared with the IOS-NA (p<0.001) and IOS-NT (p<0.001) groups separately. CONCLUSIONS: Digital scans were more accurate than conventional splinting open-trayed impressions. Prefabricated landmarks significantly improved the accuracy of full-arch implant digital scans, regardless of the scanner used. CLINICAL SIGNIFICANCE: Prefabricated landmarks can enhance the accuracy of intraoral scanners for full-arch implant rehabilitation, improving scanning efficiency and clinical outcomes.

Comparison of accuracy of hexed and nonhexed pickup impression copings in a multiple variable impression setup for recording multiple straight and angulated implant positions: An in vitro study.

Aim: The aim of this study was to evaluate and compare the accuracy of hexed and nonhexed pickup impression copings with and without splinting using polyether (PE) and polyvinyl siloxane (PVS) impression materials in open-tray technique in recording multiple straight and angulated implant positions. Settings and Design: An accurate impression results in an accurate definitive cast, thus minimizing the incidence of prosthesis misfit. The critical aspect is to record the three-dimensional location of the implant in bone rather than reproducing fine surface details. Precise fit of a fixed implant-supported prosthesis depends on the accuracy of the implant analog location within the definitive cast. Factors which affect impression accuracy include implant angulation, impression material, impression copings, technique, and splinting. Materials and Methods: A sample size of 80 study models fabricated from the impression of different groups was included. A reference master model based on All-on-4 implant concept with two parallel (implants 1 and 2) and two angulated (implant 3 at 17° and implant 4 at 30°) was fabricated using implant angulation guide. All impressions were recorded using open-tray impression technique. The groups were divided into two main groups of 40 samples each. Group A used hexed open-tray impression copings and Group B used nonhexed open-tray impression copings. Both the groups involved impression recording using splinted (Subgroup I) and nonsplinted impression copings (Subgroup II). Further, impressions in each subgroup were made using PE (Subsubgroups a) and PVS (Subsubgroup b). A total of eight subsubgroups with ten samples each were included. Impressions were recorded for each group and poured into Type IV die stone for fabrication of study models. After 24 h, the study models and reference master model were fitted with implant abutments for measurement with coordinate measuring machine. Statistical Analysis Used: The mean differences of the interimplant distance R1 (1-2), R2 (1-3), R3 (2-4), and R4 (3-4) between the reference model and sample models in different subsubgroups were calculated and three-way analysis of variance test was applied with Tukey's post hoc tests. Results: No significant difference was found in mean coronal deviations for distance R1, R2, and R3 (P > 0.05) between different study groups. P = 0.02 for R4 (distance between 17° and 30° implants) between impression materials subsubgroups suggested that significantly less distortion was created in location of highly angulated implants (>30°) using PVS impression material. Splinting and type of coping did not have a significant influence on impression accuracy. Increasing angulation decreased the accuracy. Conclusion: PVS was found equivalent in accuracy to rigid PE for recording parallel or angulated implants. Impressions of implants with higher angulations were recorded more accurately with PVS. The study found no difference in accuracy with or without splinting. Furthermore, nonhexed impression copings facilitate easier and accurate recording of multiple angulated implant location in bone.

Digital vs Conventional Full-Arch Implant Impressions: A Retrospective Analysis of 36 Edentulous Jaws.

PURPOSE: There is a paucity of comparative clinical studies assessing the accuracy of full-arch digital scans versus conventional implant impressions. The aim of this retrospective study was to compare the three-dimensional (3D) deviations between full-arch digital scans and conventional implant impressions for edentulous maxillae and mandibles. MATERIALS AND METHODS: Twenty-seven patients (36 edentulous jaws) were treated with one-piece, screw-retained implant-supported fixed complete dental prostheses (IFCDPs). Twenty-one jaws were maxillary, and 15 were mandibular. Full-arch conventional impressions and intraoral digital scans with scan bodies and an intraoral scanner had been taken during the impression phase. Following verification of the conventional stone casts, the casts were digitized. The generated standard tessellation language (STL) files from both impression techniques were merged and analyzed with reverse engineering software. The primary aim was to evaluate the accuracy between conventional and digital full-arch scans, while the effect of the edentulous jaw in 3D accuracy was the secondary aim. RESULTS: The cumulative 3D (mean ± SD) deviations between virtual casts from intraoral full-arch digital scans and digitized stone casts generated from conventional implant impressions were found to be 88 ±24 µm. In the maxillary group, the mean ± SD 3D deviation was 85 ±25 µm, compared to 92 ±23 µm for the mandibular group (p = 0.444). CONCLUSION: The 3D implant deviations found between the full-arch digital and conventional impressions lie within the clinically acceptable threshold. No statistically significant difference was identified between maxillary and mandibular jaws in terms of 3D deviations.

Complete digital workflow for prosthesis prototype fabrication with double digital scanning: A retrospective study with 45 edentulous jaws.

PURPOSE: To assess the accuracy of fit of complete-arch printed prosthesis prototypes generated with a digital workflow protocol for completely edentulous jaws. MATERIALS AND METHODS: Forty-five edentulous jaws (35 patients) underwent intraoral complete-arch digital scans with the double digital scanning (DDS) technique and the generated standard tessellation language (STL) files were superimposed and imported into computer-aided design software. After STL merging, each master STL file was used for printing a prosthesis prototype. The primary outcome was the accuracy of fit assessment of the printed prototypes on verified master stone casts. Two experienced clinicians tested the accuracy of fit with radiographs and screw-resistance tests. Secondary outcomes were the effect of the scan body shape and implant number on the accuracy of fit. RESULTS: Out of the 45 DDS-generated prosthesis prototypes, 39 presented with accurate fit on verified master stone casts, yielding an 86.70% accuracy of fit. Cylindrical scan bodies led to 100% accuracy of fit (25/25), whereas polygonal scan bodies presented with 70% accuracy of fit (14/20). Four implant-supported prostheses yielded 100% accuracy of fit (12/12), compared with 25/29 (86.30%) accuracy of fit for the six-implant-supported ones. Fisher's exact test was used to assess the effect of different scan body shapes (p = 0.005) and implant number on accuracy of fit. Chi-squared test was used to assess the association between the number of implants per arch and the accuracy of fit (p = 0.039). CONCLUSIONS: Thirty-nine out of 45 complete-arch prosthesis prototypes generated with a completely digital workflow presented with clinically acceptable fit. The effect of the scan body design and implant number was statistically significant, favoring cylindrical scan bodies and four-implant-supported prostheses.

In vivo trueness of full-arch implant-supported CAD/CAM restorations and models based on conventional impressions.

OBJECTIVES: To evaluate a method for in situ reference acquisition of implant positions in complete edentulous maxillae using an industrial scanner. To assess in vivo trueness of full-arch implant-supported fixed dentures (IFD) and dental models based on conventional impressions. METHODS: In five subjects, scan-bodies were mounted to six maxillary implants and scanned three times using an industrial scanner (REF). Original impression-based models used to manufacture existing IFDs, (MOD1), and models fabricated from new polyether impressions, (MOD2), were scanned three times with a laboratory scanner. Scan-bodies were aligned and exported with analogue positions corresponding to implant positions. Implant analogues were mounted onto existing IFDs and scanned three times (BRIDGE). CAD files of scan-bodies with inter-aligned CAD-analogues were geometry-aligned to REF. CAD-analogues were aligned to exported files of MOD1 and MOD2, and to BRIDGE. Resulting six CAD-analogues were Globally Aligned using a consistent geometry-based alignment. Deviations were computed after a Reference Point System Alignment at the implant/prosthetic platform for Cartesian axes and a linear Resultant. RESULTS: REF precision was 9.3 ± 1 µm. In vivo trueness for Resultant was MOD1: 36±16 µm, MOD2: 28±7 µm and BRIDGE: 70±23 µm, where MOD1 and MOD2 were statistically significantly different from BRIDGE. In vitro manufacturing trueness of Resultant when MOD1 acted reference for BRIDGE was: 69 ± 22. CONCLUSIONS: This method can be applied for assessing in vivo trueness. CAD/CAM processed IFD showed deviations twice that of impression-based models, however, errors from impressions and subsequent model scans were not additive to the entire workflow.

Splinting Open Tray Impression Copings Using Long Shank Carbide Burs during Definitive Impression: A Dental Technique.

AIM: To splint implant impression copings using long shank carbide burs for definitive implant impressions. BACKGROUND: The accurate transfer of the orientation recorded by impression copings to a definitive cast is a challenging step in implant prosthodontics. For achieving a passive fit from the mouth to the cast may include some discrepancies. Traditional methods of splinting can be time-consuming and troublesome to handle. TECHNIQUE: This article describes a technique by using long shank carbide burs for splinting implant impression copings. CONCLUSION: The favored implant splinting, evidence was inconclusive, and the data supporting splint pickup was the better performing technique, especially with an increased number of implants. CLINICAL SIGNIFICANCE: This technique causes minimal discomfort and is straightforward when compared to other techniques.

The effect of different implant impression splinting techniques and time on the dimensional accuracy: An in vitro study.

BACKGROUND: Splinting of impression copings is generally recommended for complex implant-supported restorations. It can also be used in the digital workflow when a control model is needed to improve the fit of the prosthesis. However, there is a lack of knowledge on how dimensional accuracy is affected by different splinting techniques and time factors. OBJECTIVES: To evaluate the time factor on the dimensional stability of different implant impression splinting techniques used in the conventional and digital workflow. MATERIALS AND METHODS: Ten pairs of implant analogs were fixed to a stainless steel bar. Modified impression copings were connected to the analogs and eight splinting strategies evaluated (n=10): (1) type I impression plaster (PLA), (2) autopolymerizing acrylic resin, cut and rejoin technique (PTR), (3) light-cured acrylic resin, cut and rejoin technique (ILC), (4) light-cured acrylic resin, no cutting and rejoining (ILN), (5) VPS bite registration material (SBR), (6) bis-acryl bite registration material (LXB), (7) bis-acryl composite resin (PTP), (8) 3D printed splint (3DP). In each group, the position of modified impression copings was scanned with a laboratory scanner at different time points: (1) unsplinted impression copings (baseline), (2) 2 h after splinting, (3) 24 h after splinting. Modified impression coping design allowed using metrology software to measure and compare distance, vertical, angle and rotational deviations between impression copings. RESULTS: All types of splints showed dimensional deviations. After 2 h of splinting, the lowest distance deviation was recorded in PTR (15.4±6.15µm), vertical deviation - in ILC (19.2±27.37µm), angle deviation - in ILC (0.08±0.1°), rotation - in LXB (0.2±0.24°) groups. Comparing results 2 and 24 h after connection of impression copings, statistically significant deviations in the distance were recorded in groups PLA (-5.6±5.95 µm), PTR (5.5±7.01µm), ILN (19.2±14.26µm), PTP (23.8±12.55µm). CONCLUSIONS: The best dimensional accuracy was observed in the ILC group, followed by PTR and 3DP groups. CLINICAL SIGNIFICANCE: Proper selection of splinting technique and polymerization time can increase the accuracy of conventional or digital impressions. Splinting techniques with rigid materials, proper polymerization and compensating for material shrinkage seem to produce the best results.